Effect of enhanced plane of nutrition in early life on the transcriptome and proteome of the anterior pituitary gland in Angus heifer calves.

BACKGROUND: Enhanced nutrition during the early calfhood period has been shown to lead to earlier pubertal development in heifer calves. This is of interest as earlier pubertal onset can subsequently facilitate earlier calving which can economically benefit production systems. Reproductive development in heifers is regulated by the hypothalamic-pituitary-ovarian signalling pathway. In particular the anterior pituitary gland is central to reproductive development, through the dynamics of gonadotropic pulsatility. However, despite clear knowledge of the influence of enhanced dietary intake on subsequent reproductive development, the molecular control governing this response in the pituitary gland within the hypothalamic-pituitary-ovarian signalling axis in heifer calves is not fully understood. The objective of this study was to examine the effect of an enhanced plane of nutrition during early life on the anterior pituitary gland of heifer calves through both transcriptomic and proteomic analyses. Between 3 and 21 weeks of age, heifer calves were offered either a high (HI, n = 14) or moderate (MOD, n = 14) plane of nutrition, designed to elicit target growth rates of 1.2 and 0.5 kg/d for HI and MOD groups, respectively. All calves were euthanised at 21 weeks of age and anterior pituitary tissue harvested for subsequent use in global transcriptomic and proteomic analyses. RESULTS: Average daily gain was affected by diet (P < 0.001) and was 1.18 and 0.50 kg/day, for HI and MOD calves, respectively. RNAseq analysis resulted in the identification of 195 differentially expressed genes (Padj<0.05; fold change > 1.5), with 277 proteins identified as differentially abundant (Padj<0.05; fold change > 1.5) between contrasting dietary treatment groups. Biochemical pathway analysis of differentially affected genes and proteins revealed an enrichment for both growth hormone and GnRH signalling pathways (Padj.<0.05). Additionally, pathway analysis predicted an effect of enhanced dietary intake on endocrine function within the anterior pituitary gland as well as on reproductive system development and function (Padj.<0.05). CONCLUSIONS: Results from this study show that an enhanced dietary intake during early calfhood affected the molecular control of the anterior pituitary gland in heifer calves in early life.

Deregulation of oxidative phosphorylation pathways in embryos derived in vitro from prepubertal and pubertal heifers based on whole-transcriptome sequencing.

BACKGROUND: Although, oocytes from prepubertal donors are known to be less developmentally competent than those from adult donors it does not restrain their ability to produce full-term pregnancies. The transcriptomic profile of embryos could be used as a predictor for embryo's individual developmental competence. The aim of the study was to compare transcriptomic profile of blastocysts derived from prepubertal and pubertal heifers oocytes. Bovine cumulus-oocyte complexes (COCs) were obtained by ovum pick- up method from prepubertal and pubertal heifers. After in vitro maturation COCs were fertilized and cultured to the blastocyst stage. Total RNA was isolated from both groups of blastocysts and RNA-seq was performed. Gene ontology analysis was performed by DAVID (Database for Annotation, Visualization and Integrated Discovery). RESULTS: A higher average blastocyst rate was obtained in the pubertal than in the pre-pubertal group. There were no differences in the quality of blastocysts between the examined groups. We identified 436 differentially expressed genes (DEGs) between blastocysts derived from researched groups, of which 247 DEGs were downregulated in blastocysts derived from pubertal compared to prepubertal heifers oocytes, and 189 DEGs were upregulated. The genes involved in mitochondrial function, including oxidative phosphorylation (OXPHOS) were found to be different in studied groups using Kyoto Encyclopedia of Genes (KEGG) pathway analysis and 8 of those DEGs were upregulated and 1 was downregulated in blastocysts derived from pubertal compared to prepubertal heifers oocytes. DEGs associated with mitochondrial function were found: ATP synthases (ATP5MF-ATP synthase membrane subunit f, ATP5PD- ATP synthase peripheral stalk subunit d, ATP12A- ATPase H+/K + transporting non-gastric alpha2 subunit), NADH dehydrogenases (NDUFS3- NADH: ubiquinone oxidoreductase subunit core subunit S3, NDUFA13- NADH: ubiquinone oxidoreductase subunit A13, NDUFA3- NADH: ubiquinone oxidoreductase subunit A3), cytochrome c oxidase (COX17), cytochrome c somatic (CYCS) and ubiquinol cytochrome c reductase core protein 1 (UQCRC1). We found lower number of apoptotic cells in blastocysts derived from oocytes collected from prepubertal than those obtained from pubertal donors. CONCLUSIONS: Despite decreased expression of genes associated with OXPHOS pathway in blastocysts from prepubertal heifers oocytes, the increased level of ATP12A together with the lower number of apoptotic cells in these blastocysts might support their survival after transfer.

Genetic and genomic evaluation of age at first calving in Italian Holsteins.

Age at first calving (AFC) represents the nonproductive period of ∼2 yr in Holstein cows, and thus, it has a relevant effect on the cost of rearing replacements in the dairy herd. In the present study, we aimed to evaluate genetic and genomic aspects of AFC in the Italian Holstein population. Data of 4,206,218 heifers with first calving between 1996 and 2020 were used. Age at first calving averaged 26.09 ± 3.07 mo and decreased across years. Heritability was estimated using a linear animal model which included the fixed effects of herd-year-season of birth and classes of gestation length, and the random animal additive genetic effect fitted to a pedigree-based relationship matrix. The EBV and genomically EBV (GEBV) were obtained, and they were standardized to mean 100 and standard deviation 5, where animals above the mean are those contributing to reduce AFC. Heritability estimates of AFC ranged from 0.031 to 0.045. The trend of sires' GEBV was favorable and indicated a reduced AFC across years. Approximate genetic correlations between GEBV of AFC and GEBV of other economically important traits were calculated on a subset of genotyped females born after 2015. Moderate favorable associations of AFC with production traits (0.39-0.51), udder depth (0.40), interval from first to last insemination in heifer (-0.43), and longevity (0.34) were assessed. Overall, the greatest lifetime productive performances and most favorable days open in first lactation were observed when heifers calved at 22 to 23 mo. In contrast, progeny of sires with GEBV of AFC above the mean yielded more milk, fat, and protein in first lactation, and had shorter days open than progeny of sires with GEBV of AFC below the mean. Results suggested that breeding strategies to improve AFC should be pursued, also considering genetic correlations between AFC and traits which are already part of the Italian Holstein breeding objective. The inclusion of AFC in an aggregate index is expected to contribute to enhance farm income.

Genome-wide association study of age at puberty and its (co)variances with fertility and stature in growing and lactating Holstein-Friesian dairy cattle.

Reproductive performance is a key determinant of cow longevity in a pasture-based, seasonal dairy system. Unfortunately, direct fertility phenotypes such as intercalving interval or pregnancy rate tend to have low heritabilities and occur relatively late in an animal's life. In contrast, age at puberty (AGEP) is a moderately heritable, early-in-life trait that may be estimated using an animal's age at first measured elevation in blood plasma progesterone (AGEP4) concentrations. Understanding the genetic architecture of AGEP4 in addition to genetic relationships between AGEP4 and fertility traits in lactating cows is important, as is its relationship with body size in the growing animal. Thus, the objectives of this research were 3-fold. First, to estimate the genetic and phenotypic (co)variances between AGEP4 and subsequent fertility during first and second lactations. Second, to quantify the associations between AGEP4 and height, length, and BW measured when animals were approximately 11 mo old (standard deviation = 0.5). Third, to identify genomic regions that are likely to be associated with variation in AGEP4. We measured AGEP4, height, length, and BW in approximately 5,000 Holstein-Friesian or Holstein-Friesian × Jersey crossbred yearling heifers across 54 pasture-based herds managed in seasonal calving farm systems. We also obtained calving rate (CR42, success or failure to calve within the first 42 d of the seasonal calving period), breeding rate (PB21, success or failure to be presented for breeding within the first 21 d of the seasonal breeding period) and pregnancy rate (PR42, success or failure to become pregnant within the first 42 d of the seasonal breeding period) phenotypes from their first and second lactations. The animals were genotyped using the Weatherby's Versa 50K SNP array (Illumina, San Diego, CA). The estimated heritabilities of AGEP4, height, length, and BW were 0.34 (90% credibility interval [CRI]: 0.30, 0.37), 0.28 (90% CRI: 0.25, 0.31), 0.21 (90% CRI: 0.18, 0.23), and 0.33 (90% CRI: 0.30, 0.36), respectively. In contrast, the heritabilities of CR42, PB21 and PR42 were all <0.05 in both first and second lactations. The genetic correlations between AGEP4 and these fertility traits were generally moderate, ranging from 0.11 to 0.60, whereas genetic correlations between AGEP4 and yearling body-conformation traits ranged from 0.02 to 0.28. Our GWAS highlighted a genomic window on chromosome 5 that was strongly associated with variation in AGEP4. We also identified 4 regions, located on chromosomes 14, 6, 1, and 11 (in order of decreasing importance), that exhibited suggestive associations with AGEP4. Our results show that AGEP4 is a reasonable predictor of estimated breeding values for fertility traits in lactating cows. Although the GWAS provided insights into genetic mechanisms underpinning AGEP4, further work is required to test genomic predictions of fertility that use this information.

Effects of calving interval of dairy cows on development, metabolism and milk performance of their offspring.

Extending the voluntary waiting period (VWP) for insemination in dairy cows is of interest to reduce the frequency of calving events and inseminate at a moment with fewer fertility problems. Little is known about the calves born from dams with a different VWP followed by a different calving interval (CInt). The objective of the current study was to identify the effect of dam's CInt on body condition, metabolic status, and milk production of their offspring from birth till 100 DIM of the offspring's first lactation. Holstein Friesian dairy cows (n = 154, 41 primiparous, 113 multiparous) were blocked according to parity, milk yield, and somatic cell count (SCC), and randomly assigned to a VWP of 50, 125, or 200 d. Female calves (n = 62) from cows with different CInt were monitored from birth until their first calving event as heifer. Certain dams were not successfully inseminated soon after the planned VWP, resulting in differences between the intended VWP and the actual CInt. Calves were regrouped according to their dam's actual CInt (CInt_1: 324 - 408 d; CInt_2: 409 - 468 d; CInt_3: 469 - 586 d). The dam's CInt did not affect calf birth weight. From birth to weaning, the calves born to dams in CInt_1 (0.34 mmol/L (confidence interval (CI): 0.30, 0.37) had a higher plasma nonesterified fatty acids (NEFA) concentration than CInt_2 (0.28 mmol/L (CI: 0.26, 0.31)) and CInt_3 (0.26 mmol/L (CI: 0.24, 0.29)) calves. Calves born to dams with a shorter CInt (CInt_1) had greater IgG and IgM against keyhole limpet hemocyanin (KLH) than CInt_3 (IgG: 6.05 ± 0.30 vs. 4.64 ± 0.30; IgM: 6.45 ± 0.17 vs. 5.89 ± 0.16, respectively) before weaning. After weaning till calving, CInt_1-calves tended to have greater plasma NEFA concentration than CInt_3-calves. During the first 100 d in milk, a longer CInt of the dams resulted in lower plasma IGF_1 (CInt_2), lower milk lactose (CInt_3) and fat and protein corrected milk (FPCM) (CInt_2) in offspring, compared with shorter CInt of the dams (CInt_1). Collectively, a longer CInt in dams did not affect birth weight of their calves or body weight during the weaning or rearing phase. From birth till weaning, a longer CInt in dams resulted in less IgG against KLH and lower plasma NEFA concentration in plasma of the calves. During the first lactation of their offspring, a longer CInt in dams can result in a lower plasma IGF_1 and FPCM during the first 100 DIM, although effects were not present in all CInt categories.

A dynamic individual method for yak heifer live body weight estimation using the YOLOv8 network and body parameter detection algorithm.

Live body weight (LBW) is one of the most important parameters for supervising the growth and development of livestock. The yak (Bos grunniens) is a special species of cattle that lives on the Qinghai-Tibetan Plateau. Yaks are more untamed than regular cattle breeds, so it is more challenging to measure their LBW. In this study, YOLOv8 yak detection and LBW estimation models were used to automatically estimate yak LBW in real time. First, the proper posture (normal posture) and individual yak identification was confirmed and then the YOLOv8 detection model was used for LBW estimation from 2-dimensional images. Yak LBW was estimated through yak body parameter extraction and a simple linear regression between the estimated yak LBW and the actual measured yak LBW. The results showed that the overall detection performance for normal yak posture was described by precision, recall, and mean average precision 50 (mAP50) indicators, reaching 81.8%, 86.0%, and 90.6%, respectively. The best yak identification results were represented by precision, recall, and mAP50 values of 97.8%, 96.4%, and 99.0%, respectively. The yak LBW estimation model achieved better results for the 12-mo-old yaks with shorter hair, with values for R2, root mean square error, mean absolute percentage error, and multiple R of 0.96, 2.43 kg, 1.69%, and 0.98, respectively. The results demonstrate that yak LBW can be estimated and monitored in real time using this approach. This study has the potential to be used for daily yak LBW monitoring in an unstressed manner and to save considerable labor resources for large-scale livestock farms. In the future, to reduce the limitations caused by the impacts of yak hair and light condition, datasets of dairy cows and yaks of different ages will be used to improve and generalize the model.

Association between maternal growth in the pre-conception and early gestational period of nulliparous dairy heifers with anti-Müllerian hormone in their female offspring.

Anti-Müllerian hormone (AMH) is secreted by granulosa cells of healthy, growing follicles and is positively correlated with the ovarian reserve. Maternal and environmental factors, such as nutrition, disease, parity and endocrine disruptors, are thought to have a profound impact on ovarian reserve development during early foetal life. For genetic progress, it can be advantageous to breed dairy replacements from heifers to expedite the generation interval; however, there is some evidence that nulliparous animals produce female offspring with smaller ovarian reserves compared with multiparous animals. The objective of this prospective, observational study was to determine whether maternal growth in the pre-conception and early gestational period of nulliparous dairy heifers is associated with pre-weaning AMH concentrations in their female offspring. Our hypothesis was that excessive growth in this period would negatively impact AMH concentrations. Seasonal, pasture-based dairy heifer calves (n = 156) born from nulliparous dams, from six Irish farms, were blood sampled at an average of 60 days of age in spring 2022 and tested for AMH. Mixed-effects linear regression models were constructed with Box-Cox transformed AMH concentration as the dependent variable. The independent variables tested included maternal average daily gain (ADG) from pre-breeding examination (PBE) to pregnancy diagnosis (PD) between 30 and 60 days in calf (DIC), ADG from PBE to PD over 60 DIC and ADG between the two PDs. Calf breed and age at sampling were forced into the models, and the farm was treated as a random effect in all models. We found that as ADG increased from the pre-breeding period to their first PD visit, the AMH concentration in their offspring reduced. However, ADG explained only a small amount of the variation in AMH concentrations (marginal R2 = 0.041). In conclusion, the results of our study suggest that excessive growth prior to conception and in early gestation of nulliparous heifers could impact the ovarian reserve of their female offspring, and may imply that farmers should avoid excessive growth in the immediate pre-breeding and early gestational periods.

Anti-Müllerian hormone: A novel biomarker for detecting bovine freemartinism.

The anti-Müllerian hormone (AMH) indicates ovarian reserve in cattle, maintaining a consistent trajectory post-puberty. In heterosexual pregnancies, the development of the Müllerian duct in female foetuses is inhibited, resulting in an anticipated minimal or absent ovarian reserve capacity. This investigation aimed to compare AMH levels in healthy Holstein heifers that had reached puberty with those of freemartin animals of the same breed and age. The study incorporated Holstein heifers reaching puberty between 11 and 15 months of age in Group 1 (G1, n = 20) and freemartin animals in Group 2 (G2, n = 19, 16). AMH measurements (AMH-1/AMH-2) were recorded at 12-day intervals for the study participants. Notably, AMH levels in three freemartin animals could not be detected, prompting statistical analysis based on measurements from the remaining 16 freemartin animals in G2. A statistically significant correlation was observed between two separate measurements in G1 and G2 (p < .001). Furthermore, AMH-1 and AMH-2 levels were statistically higher in G1 than in G2 (p < .001). In G1, AMH-1 levels ranged from 227 to 677 pg/mL, with an average of 367.3 ± 25.5 pg/mL, and AMH-2 levels ranged from 234 to 645 pg/mL, with an average of 380.8 ± 24.4 pg/mL. Conversely, in G2, AMH-1 levels ranged from 10 to 72 pg/mL, with an average of 26.8 ± 4.44 pg/mL, and AMH-2 levels ranged from 12 to 68 pg/mL, with an average of 28.75 ± 4.18 pg/mL. The mean AMH levels in G1 were approximately 14 times higher than in G2 (p < .001). Consequently, ROC analysis utilizing AMH-1 and AMH-2 data established cut-off values of ≤72 and ≤ 68 pg/mL respectively for distinguishing freemartin animals. In conclusion, AMH could be used as a reliable biomarker for identifying Holstein freemartin animals.

Genome-wide association analysis of heifer livability and early first calving in Holstein cattle.

BACKGROUND: The survival and fertility of heifers are critical factors for the success of dairy farms. The mortality of heifers poses a significant challenge to the management and profitability of the dairy industry. In dairy farming, achieving early first calving of heifers is also essential for optimal productivity and sustainability. Recently, Council on Dairy Cattle Breeding (CDCB) and USDA have developed new evaluations of heifer health and fertility traits. However, the genetic basis of these traits has yet to be thoroughly studied. RESULTS: Leveraging the extensive U.S dairy genomic database maintained at CDCB, we conducted large-scale GWAS analyses of two heifer traits, livability and early first calving. Despite the large sample size, we found no major QTL for heifer livability. However, we identified a major QTL in the bovine MHC region associated with early first calving. Our GO analysis based on nearby genes detected 91 significant GO terms with a large proportion related to the immune system. This QTL in the MHC region was also confirmed in the analysis of 27 K bull with imputed sequence variants. Since these traits have few major QTL, we evaluated the genome-wide distribution of GWAS signals across different functional genomics categories. For heifer livability, we observed significant enrichment in promotor and enhancer-related regions. For early calving, we found more associations in active TSS, active Elements, and Insulator. We also identified significant enrichment of CDS and conserved variants in the GWAS results of both traits. By linking GWAS results and transcriptome data from the CattleGTEx project via TWAS, we detected four and 23 significant gene-trait association pairs for heifer livability and early calving, respectively. Interestingly, we discovered six genes for early calving in the Bovine MHC region, including two genes in lymph node tissue and one gene each in blood, adipose, hypothalamus, and leukocyte. CONCLUSION: Our large-scale GWAS analyses of two heifer traits identified a major QTL in the bovine MHC region for early first calving. Additional functional enrichment and TWAS analyses confirmed the MHC QTL with relevant biological evidence. Our results revealed the complex genetic basis of heifer health and fertility traits and indicated a potential connection between the immune system and reproduction in cattle.

Interaction of pre- and postnatal nutrition on expression of leptin receptor variants and transporter molecules, leptin transport, and functional response to leptin in heifers†.

Perinatal nutrition modulates the hypothalamic neurocircuitries controlling GnRH release, thus programming pubertal maturation in female mammals. Objectives of experiments reported here were to test the hypotheses that prenatal nutrition during mid- to late gestation interacts with postnatal nutrition during the juvenile period in heifer offspring to alter expression of leptin receptor (LepR) variants (ObRa, ObRb, ObRc, ObRt), and lipoprotein transporter molecules (LRP1 and 2) in the choroid plexus, leptin transport across the blood-brain barrier, and hypothalamic-hypophyseal responsiveness to exogenous ovine leptin (oleptin) during fasting. Nutritional programming of heifers employed a 3 × 2 factorial design of maternal (high, H; low, L; and moderate, M) × postnatal (H and L) dietary treatments. Results (Expt. 1) demonstrated that prepubertal heifers born to L dams, regardless of postnatal diet, had reduced expression of the short isoform of ObRc compared to H and M dams, with sporadic effects of undernutrition (L or LL) on ObRb, ObRt, and LRP1. Intravenous administration of oleptin to a selected postpubertal group (HH, MH, LL) of ovariectomized, estradiol-implanted heifers fasted for 56 h (Expt. 2) did not create detectable increases in third ventricle cerebrospinal fluid but increased gonadotropin secretion in all nutritional groups tested. Previous work has shown that leptin enhances gonadotropin secretion during fasting via effects at both hypothalamic and anterior pituitary levels in cattle. Given the apparent lack of robust transfer of leptin across the blood-brain barrier in the current study, effects of leptin at the adenohypophyseal level may predominate in this experimental model.

Association of age at first calving with longevity, milk yield, and fertility up to the third lactation in a herd of Holstein dairy cows in Japan.

Accelerating age at first calving (AFC) is a strategy for sustainable dairy farming, whereas the impact of a reduction in AFC on long-term performance remains unclear. In this study, longevity and milk productivity until the end of the third lactation period were investigated retrospectively according to AFC. A total of 169 cows were categorized according to AFC as young, moderate, old, and very old (< 22.5, 22.5 -< 24.0, 24.0 -< 25.5, and > 25.5 months). The young AFC group had approximately 70 kg lower body weight before first calving (620 vs. 695 kg, P < 0.05) and experienced their first calving approximately 4.2 months earlier than the very old AFC group (21.9 vs. 26.1 months, P < 0.05). The survival rate at the third calving stage was 61% in the young AFC group, which was higher than those in the moderate (42%), old (35%), and very old (33%) AFC groups. In the young AFC group, no cows were culled because of low productivity and hoof disease, compared to 5.0-8.1% of older AFC cows. The young AFC group had a higher overall lifetime milk yield (cumulative milk yield/days from birth to the end of final lactation) than the old AFC group (14.3 vs. 8.7 kg/d, P = 0.11). The cows that survived the third calving had better reproductive performance than non-surviving cows; however, no statistical difference was detected among the AFC groups. In conclusion, AFC as early as 22.5 months could be associated with better survivability and higher overall lifetime milk yield than older AFC without impairing reproductive performance. Our results suggest that accelerating AFC may lead to higher profitability.

Histological tissue structure alterations resulting from Staphylococcus aureus intramammary infection in heifer mammary glands hormonally induced to rapidly grow and develop.

Intramammary infections (IMI) are common in nonlactating dairy cattle and are expected to impair mammary growth and development and reduce future milk production. The objective of this study was to histologically evaluate how IMI alter tissue structure in growing and developing heifer mammary glands. A total of 18 nonpregnant, nonlactating heifers between 11 and 14 mo of age were used in the present study. Heifers received daily supraphysiological injections of estradiol and progesterone for 14 d to stimulate rapid mammary growth and development. One-quarter of each heifer was subsequently infused with Staphylococcus aureus (CHALL) while a second quarter served as an uninfected control (UNINF). Heifers were randomly selected and euthanized either the last day of hormonal injections to observe IMI effects on mammary gland growth (GRO), or 13 d post-injections, to observe IMI effects on mammary development (DEV). Mammary tissues were collected from the center and edge parenchymal regions of each mammary gland for morphometric tissue area evaluation. For GRO tissues, CHALL quarters had less epithelial tissue area and marginally more intralobular stroma tissue area than UNINF quarters. Tissue areas occupied by luminal space, extralobular stroma, adipose, and lobular tissue were similar. For DEV tissues, area occupied by epithelium, luminal space, intralobular stroma, and extralobular stroma did not differ between quarter treatments, but UNINF quarters had more adipose tissue area and marginally less lobular area than CHALL quarters. Results indicate that IMI in growing and developing mammary glands reduces mammary epithelial growth and alters mammary gland development by impairing epithelial branching into the mammary fat pad. Taken together, these tissue changes before calving may have adverse effects on milk production. Therefore, an important focus should be placed on improving udder health in replacement heifers through management strategies that mitigate the deleterious effects of IMI and promote the positive development of the mammary gland.

Limit feeding total mixed rations exacerbates intersucking in year-old dairy heifers.

Limit feeding is a practice that is used to improve feed efficiency and control growth in dairy heifers, but also has negative consequences associated with hunger and restriction of feeding behavior. One such consequence could be intersucking (i.e., the licking or sucking of another animal's teats or udder). This behavior is reported to varying degrees in heifers, and thus, our first objective was to evaluate whether intersucking increased in response to short-term (48 h) feed restriction. Intersucking interventions, such as nose rings, are often applied to specific animals, and so our second objective was to describe intersucking performance in individual heifers, including those that represent outliers in this population. We studied 42 heifers (9 Jerseys, 33 Holsteins) aged 12.8 ± 1.1 mo (mean ± SD). They were housed in 21 pairs, the experimental unit for our first objective. We used a switchback design with 3 periods of 2 d each where heifers were fed ad libitum total mixed ration in the first and third periods (Baseline and Return, respectively), and limit fed to 50% of ad libitum intake in the second period (Restriction). We scored time spent intersucking continuously and eating at 5-min intervals from video recordings from 0800 to 2000 h on 4 d (baseline d 2, restriction d 2, return d 1, and return d 2). Heifer pairs spent less time eating (16 ± 0.4% mean percentage of 12-h observations ± SE), more time intersucking (27 ± 7 s/12 h), and engaged in longer bouts of intersucking (23 ± 5 s/bout) on Restriction d 2 compared with all other days (eating: 34.7 ± 1.1%, 44.2 ± 0.9%, 35.8 ± 1.1% of 12-h; intersucking time: 7 ± 2, 7 ± 3, 10 ± 5 s/12 h; intersucking bout length: 3 ± 1, 2 ± 1, 3 ± 1 s/bout; Baseline d 2, Return d 1, Return d 2, respectively). There was no difference in the number of bouts of intersucking across days (1.3 ± 0.2 bouts/12 h). The drop in eating during feed restriction was followed by a rebound on Return d 1 before returning to baseline levels. Time spent intersucking did not differ among ad libitum periods. Overall, 90% of the heifers performed intersucking on at least 1 of the 4 d, and did this for 1 to 127 s/12 h (range) in 1 to 13 bouts/12 h. Of the heifers that intersucked, 55% did this at extreme levels relative to the rest of the experimental population (outliers). Solid feed restriction exacerbated intersucking in year-old heifers, but this behavior was widespread.

l-Glutamine supplementation reduces gastrointestinal permeability and biomarkers of physiological stress in preweaning Holstein heifer calves.

l-Glutamine supplementation improves gastrointestinal and immune function in dairy calves during controlled immune and stress challenges. However, it is unknown whether supplementing milk replacer (MR) with l-glutamine improves preweaning dairy calf health and welfare under production conditions. Therefore, the study objective was to evaluate the effects of supplementing MR with l-glutamine on gastrointestinal permeability, immune function, growth performance, postabsorptive metabolic biomarkers, and physiological stress response in preweaning dairy calves. In 3 repetitions, Holstein heifer calves (n = 30; 1.5 ± 0.5 d old; 37.1 ± 0.86 kg body weight) were blocked by serum total protein, body weight, and age, and provided MR (3.8 L/calf per d; 24% CP, 17% fat, 12.5% solids) supplemented with l-glutamine (GLN; 10g/kg MR powder; n = 5 calves/repetition) or nonsupplemented (NSMR; n = 5 calves/repetition). Calves were individually housed with ad libitum starter grain and water access until weaning (56.4 ± 0.5 d old). At 1 and 6 wk of age, urinary catheters were placed, and calves were orally dosed with 1 L of chromium (Cr)-EDTA. Urine samples were collected over a 24-h period for Cr output analysis as an in vivo biomarker of gastrointestinal permeability. Blood was collected on study d 1, 5, 7, 14, 21, 42, and 56 to measure white blood cell counts, cortisol, insulin, glucose, nonesterified fatty acids, serum amyloid A, haptoglobin, and neutrophil: lymphocytes. Two study intervals were used in the statistical analyses, representing greater (P1; wk 1-3) and reduced (P2; wk 4-8) enteric disease susceptibility. Data were analyzed using PROC GLIMMIX in SAS 9.4 (SAS Institute Inc.) with calf as the experimental unit. Overall, total urinary Cr output was reduced in GLN versus NSMR calves. Total Cr output was reduced at 1 wk of age in GLN versus NSMR calves, but no differences were detected at 6 wk of age. Neutrophil:lymphocyte was decreased both overall and during P2 in GLN versus NSMR calves, and neutrophil counts tended to be reduced in GLN versus NSMR calves during P2. No MR treatment differences were detected for average daily feed intake, average daily gain, body measurements, postabsorptive metabolic biomarkers, disease scores, and therapeutic treatments between GLN and NSMR calves. In summary, l-glutamine supplementation reduced gastrointestinal permeability and biomarkers of physiological stress in preweaning Holstein heifer calves.

The effect of progesterone concentrations during superovulation of Holstein heifers in a randomized trial.

The aim of this study was to evaluate the effect of different progesterone (P4) concentrations during the follicular growth on the intensity of estrous expression, ovarian response to the superovulatory treatment, and embryo production and quality in superovulated heifers. A total of 63 Holstein heifers were randomly assigned into 2 experimental groups: Low P4 (n = 31) and High P4 (n = 32). Animals received a pre-synchronization protocol followed by a protocol of superovulation that included the allocated P4 treatment. Activity was monitored continuously by an automated activity monitor, and estrus characteristics (maximum intensity and duration) were recorded. Embryo collection was performed 7 d post artificial insemination (AI). Embryos were counted and graded from good or excellent (1) to degenerated (4). The outcomes of interest were: number and diameter of follicles at the time of AI, ovulation success (confirmed 7 d post-AI), time to estrus event, maximum intensity and duration of estrus, number and quality of embryos. Data were analyzed according to the type of outcome variable using logistic, linear, or Poisson regression models. A total of 105 embryos (High P4: n = 42; Low P4: n = 63) were graded for quality. Different P4 levels did not affect the maximum intensity (High P4 = 497.8 ± 23.9%; Low P4 = 542.2 ± 23.5%) or the duration (High P4 = 13.5 ± 1.5 h; Low P4 = 14.3 ± 1.4 h) of estrus. Heifers in the High P4 treatment had greater number of follicles at time of AI (High P4 = 16.6 ± 1.6 follicles; Low P4 = 13.9 ± 1.2 follicles), but with smaller diameter (High P4 = 11.3 ± 0.1 mm; Low P4 = 12.0 ± 0.1 mm) compared with Low P4. High P4 heifers tended to have better embryo quality compared with Low P4 heifers (odds ratio = 1.98; 95% CI = 0.90-4.35). High P4 heifers had less embryos than Low P4 heifers, but this was modified by the CIDR (intravaginal implant of P4) removal to estrus interval (interval 0-21 h: mean ratio = 1.15, 95% CI = 0.42-1.87; interval 22-46 h: mean ratio = 0.58, 95% CI = 0.27-0.96). Although estrous expression was not associated with embryo quality, as the duration and the maximum intensity of estrous expression increased, the number of embryos recovered 7 d post-AI increased (duration: mean ratio = 1.04; 95% CI = 1.03-1.05; maximum intensity: mean ratio = 1.50; 95% CI = 1.42-1.58). In conclusion, P4 during the follicular growth, and intensity of estrus, are playing a role in regulating the quality and the number of embryos produced by superovulated heifers. This study was supported by contributions from Resilient Dairy Genome Project and the Natural Sciences and Engineering Research Council.

Genomic evaluation of feed efficiency in US Holstein heifers.

There is growing interest in improving feed efficiency traits in dairy cattle. The objectives of this study were to estimate the genetic parameters of residual feed intake (RFI) and its component traits [dry matter intake (DMI), metabolic body weight (MBW), and average daily gain (ADG)] in Holstein heifers, and to develop a system for genomic evaluation for RFI in Holstein dairy calves. The RFI data were collected from 6,563 growing Holstein heifers (initial body weight = 261 ± 52 kg; initial age = 266 ± 42 d) for 70 d, across 182 trials conducted between 2014 and 2022 at the STgenetics Ohio Heifer Center (South Charleston, OH) as part of the EcoFeed program, which aims to improve feed efficiency by genetic selection. The RFI was estimated as the difference between a heifer's actual feed intake and expected feed intake, which was determined by regression of DMI against midpoint MBW, age, and ADG across each trial. A total of 61,283 SNPs were used in genomic analyses. Animals with phenotypes and genotypes were used as training population, and 4 groups of prediction population, each with 2,000 animals, were selected from a pool of Holstein animals with genotypes, based on their relationship with the training population. All traits were analyzed using univariate animal model in DMU version 6 software. Pedigree information and genomic information were used to specify genetic relationships to estimate the variance components and genomic estimated breeding values (GEBV), respectively. Breeding values of the prediction population were estimated by using the 2-step approach: deriving the prediction equation of GEBV from the training population for estimation of GEBV of prediction population with only genotypes. Reliability of breeding values was obtained by approximation based on partitioning a function of the accuracy of training population GEBV and magnitudes of genomic relationships between individuals in the training and prediction population. Heifers had DMI (mean ± SD) of 8.11 ± 1.59 kg over the trial period, with growth rate of 1.08 ± 0.25 kg/d. The heritability estimates (mean ± SE) of RFI, MBW, DMI, and growth rate were 0.24 ± 0.02, 0.23 ± 0.02, 0.27 ± 0.02, and 0.19 ± 0.02, respectively. The range of genomic predicted transmitted abilities (gPTA) of the training population (-0.94 to 0.75) was higher compared with the range of gPTA (-0.82 to 0.73) of different groups of prediction population. Average reliability of breeding values from the training population was 58%, and that of prediction population was 39%. The genomic prediction of RFI provides new tools to select for feed efficiency of heifers. Future research should be directed to find the relationship between RFI of heifers and cows, to select individuals based on their lifetime production efficiencies.

Supplementing sodium butyrate to limit-fed heifers: Effects on growth, coccidiosis, urinary purine derivatives, and apparent total-tract nutrient digestibility.

The objective of this study was to assess the growth, apparent total-tract digestibility of nutrients, the prevalence of coccidia, and purine derivatives in postweaning heifers when limit-fed a diet supplemented with sodium butyrate (SB). A 12 wk randomized complete block experiment was conducted using 24 Holstein heifers (92.8 d ± 1.9 d of age and initial body weight [BW] of 99.6 ± 15.2 kg [mean ± standard deviation]). Treatments were 100 g soybean meal (control; CON) and 0.75 g of SB/kg of BW + 100 g soybean meal (SB). Diets were formulated to contain 16.4% crude protein, 2.27 Mcal/kg metabolizable energy (ME), and fed at a feed out rate of 2.15% of BW on a dry matter basis. Intakes were recorded daily while growth measurements and BW were recorded weekly. Urine and fecal samples were taken every 2 wk. On d 42 through d 49 an apparent total-tract digestibility phase took place using acid detergent insoluble ash as a marker. Growth measurements were similar among treatments except CON heifers grew longer and tended to be taller at the withers. A trend was observed for CON animals to have lower levels of coccidian oocytes by week. Heifers fed SB had lower blood glucose levels and higher levels of ketones in their blood. Urinary volume was greater for heifers fed SB throughout the 12 wk study. Total purine derivatives were greater in CON heifers. Dry matter, organic matter and acid detergent fiber digestibilities were greater for heifers fed SB compared with CON heifers. Crude protein, neutral detergent fiber, and ash digestibilities tended to be greater in heifers fed SB than in CON heifers. These results suggested no growth benefit of supplementing SB to limit-fed heifers; however, apparent total-tract fiber, ash, and crude protein digestibilities were improved in the SB fed heifers likely due to improved ruminal and intestinal development.

Effects of vitamin E and selenium administration on transportation stress in pregnant dairy heifers.

We investigated the effects of road transportation and administration of the vitamin E and selenium (ESe) on circulating cortisol, haptoglobin, blood metabolites, oxidative biomarkers, white blood cell profiles, and behaviors in pregnant dairy heifers. Forty pregnant Holstein heifers were randomly assigned to one of 4 treatments: no transportation and no ESe administration, no transportation and ESe administration, transportation and no administration, and transportation and ESe administration. The ESe (70 IU/kg dry matter feed of dl-α-tocopheryl acetate and 0.3 mg/kg dry matter feed of sodium selenite) was orally delivered once a day from 7 d before transportation to 3 d after transportation. The heifers were transported in trucks designed for cattle transportation. Blood was collected 1 h before transportation, immediately after transportation (IAT), and at 6, 24, and 48 h after transportation. Behaviors were recorded using a video camera for 2 consecutive days after transportation. Transported/non-ESe-administered heifers had greater cortisol at IAT, haptoglobin at 6 and 24 h after transportation, total oxidative status at 6 h after transportation, and nonesterified fatty acid levels, white blood cell numbers, and neutrophil percentages at IAT and 6 h after transportation in the blood than nontransported heifers. Transported/non-ESe-administered heifers had lower total antioxidative status levels at 48 h after transportation and lymphocyte percentages at IAT and 6 h after transportation than nontransported heifers. Lying time was shorter in transported heifers than nontransported/non-ESe-administered heifers. Transported/ESe-administered heifers had lower cortisol, total oxidative status, nonesterified fatty acid levels at IAT, and haptoglobin concentrations at 6 and 24 h after transportation than transported/non-ESe-administered heifers. Transported/ESe-administered heifers had greater total antioxidative status levels at 48 h after transportation than transported/non-ESe-administered heifers. No ESe administration effects were observed for white blood cell number and neutrophil and lymphocyte percentages and lying time. In conclusion, road transportation caused temporary oxidative stress. Administrating ESe partially alleviated the stress, suggesting that ESe administration could be a viable strategy to reduce stress in transported pregnant heifers, providing a novel role of vitamin E and selenium for improving animal welfare.

Heat ameliorative measures in Murrah buffalo (Bubalus bubalis) heifers during summer: effect on microclimate, thermal comfort, and behavior.

Water buffalo (Bubalus bubalis) is the mainstay of milk production in Asian countries including India. However, the hot climate of the country remains the biggest bottleneck to exploit the potential of this species. Therefore, a study was conducted to assess the effect of heat ameliorative measures on microclimate, thermal comfort, and behavior of Murrah buffalo heifers during summer. Buffalo heifers (n = 24) between the age of 15 and 20 months with a mean body weight of 363.75 ± 11.27 kg were randomly grouped into four treatments based on their age and body weight. The heifers kept in the shed without any cooling served as CON (control), while the animals of group CJ were tied with a cooling jacket. The buffalo heifers of the CJF group were subjected to the cooling jacket with forced air ventilation, whereas the intermittent (10 min at 2-h intervals) sprinkling followed by forced air ventilation was practiced in group SF between 900 and 1800 h throughout the experiment. The microclimatic variables were low in the sheds of groups CJ, CJF, and SF than the CON. The physiological responses such as rectal temperature, skin temperature, respiration rate, and pulse rate were reduced in groups CJ, CJF, and SF than the CON at 1400 h. The serum cortisol was less in the CJF and SF than those of CON group. The animals of the CJ, CJF, and SF groups spent more time for feeding and rumination with less frequent longer bouts. The extended periods of lying followed by shorter standing and idling were observed in groups CJ, CJF, and SF when compared with the CON. It may be therefore concluded that cooling jacket and intermittent sprinkling in combination with forced air ventilation might be helpful in improving the micro-environment, thermal comfort, and behavior of buffalo heifers particularly under tropical climates during summer.

Evaluation of serum anti-Müllerian hormone concentrations following treatment with vitamin D in Holstein Friesian heifers.

Anti-Müllerian hormone (AMH) levels in the blood of dairy cattle are associated with the count of antral follicles (AFC), ovarian function. Numerous studies, particularly in human medicine, have shown that vitamin D3 (Vit D3) has a positive effect on AMH levels. To our knowledge, the effects of Vit D3 on serum AMH levels in heifers have not been investigated. The goal of the current study was to evaluate the concentrations of serum AMH in dairy heifers following Vit D3 treatment. The study included 20 healthy non-pregnant Holstein Friesian heifers. These animals came to estrus at least once. All heifers received a single intramuscular dosage of 5 million IU Vit D3 (Cholecalciferol). Blood samples were collected from the coccygeal veins of all animals before and after Vit D3 injection (days 7, 14, and 28) for the measurement of AMH and 25(OH)D concentrations. In our analysis, we observed that after exogenous Vit D3 administration, circular 25(OH)D increased constantly (up to day 28 after Vit D3 injection) in all animals. On day 28, AMH concentrations saw a 10% increase in comparison with those measured the day before the Vit D3 injection. However, a comparison of AMH concentrations measured across days did not reveal statistically significant differences between Day 0, 7, 14, and 28 levels (p = .10). Furthermore, no statistical correlation was observed between the pairs (age-AMH) and (weight-AMH). Considering all times, no correlation was found between 25(OH)D and blood AMH levels. These findings demonstrated that exogenous Vit D3 did not affect serum AMH in Holstein Friesian heifers.